This is a caterpillar, tightly curled-up for insulation and/or protection from predators. Multiple species of moth and butterfly overwinter as caterpillars in our area. Given its size, bristly covering, black color and red body segments, this looks like a Giant Leopard Moth caterpillar in particular, but it's hard to say for sure since several species can look very similar. (There are over two thousand species of moths found in Maryland.) You can view some examples of Giant Leopard Moth caterpillars for comparison about two-thirds of the way down the gallery page on Maryland Biodiversity Project's page for this species. They are not considered a garden pest, so you can put it back to continue sheltering in leaf litter until it's ready to transform into an adult moth.

Miri

You're welcome. It's ok, predation is part of the natural cycle, and these moths are not rare. Spiders are great garden predators to keep around, so if you find any in the future, try to let them be so they can help you control garden pests. (The only large ones likely to be seen hunting on the ground are wolf spiders and their relatives. Despite the foreboding name, they don't harm people.)

Miri